Chemopreventive efficacies of rosiglitazone, fenretinide and their combination against rat mammary carcinogenesis.

INTRODUCTION: Peroxisome proliferator-activated receptor gamma (PPAR-gamma) and retinoic acid receptors (RAR/RXR) belong to the nuclear steroid receptor family. In vitro studies have suggested that PPAR-gamma ligands are highly effective in preventing mammary tumours and these effects are enhanced by some retinoids. However, in vivo anti-initiator and anti-promoter efficacies of this combination are not clear. AIM AND METHODS: The present study aimed to investigate the chemopreventive efficacies of the PPAR-gamma ligand rosiglitazone (200 microg/kg/day), synthetic retinoid fenretinide (0.3 mg/kg/day) and their combination on a DMBA-induced rat mammary carcinogenesis model. RESULTS: In the rosiglitazone group, no malignant tumour developed, apart from the lowest proliferative mammary lesions. In the fenretinide group, 30% developed a malignant tumour but there were no benign tumours. Cancer incidences were 61.5% and 10% in the control and combination groups respectively. CONCLUSIONS: Our results showed that the PPAR-gamma ligand rosiglitazone and synthetic retinoid fenretinide have potent chemopreventive properties against in vivo mammary carcinogenesis; however, the efficacies were not enhanced by their combination.

Effects of oral L-arginine supplementation on blood pressure and asymmetric dimethylarginine in stress-induced preeclamptic rats.

This study was carried out to elucidate the role of asymmetric dimethylarginine (ADMA) and nitric oxide (NO) in preeclampsia development, and to investigate the effect of L-arginine supplementation in rats. Preeclampsia was induced in pregnant rats using a stress model. L-arginine was administered orally and ADMA, urinary nitrate, and protein levels were measured on the 20th day of pregnancy. Compared with the group of rats that are normally pregnant, the levels of blood pressure (BP), protein excretion, and ADMA were significantly increased in preeclampsia which returned to normal levels following the supplementation of L-arginine. Both group of rats had similar urine nitrate levels. Arginine-ADMA-NO pathway is affected in preeclampsia. L-arginine supplementation decreased hypertension (HT), proteinuria, and ADMA levels indicating that taking L-arginine may be beneficial in preeclampsia treatment.

Increased inositol-monophosphatase activity by lithium treatment in bipolar patients.

Inhibition of inositol monophosphatase (IMPase) enzyme is the target mechanism of action of lithium. However, increased activity of mRNA levels by lithium has been reported. These two diverse effects were shown after relatively short periods of lithium administration. The aim of this study was to observe the effect of prolonged use of lithium on IMPase activity. The authors investigated IMPase activities in fresh erythrocytes and leukocytes in 63 bipolar patients (42 euthymic, 8 depressive, 13 manic episodes) and 16 control subjects. We found that erythrocyte IMPase activity was higher in lithium treated euthymic patients than non-lithium treated patients. The duration of lithium use was positively correlated with leukocyte IMPase activity. Increased IMPase activity by chronic lithium use suggests an up-regulation of the enzyme activity.

The protective effects of resveratrol on human coronary artery endothelial cell damage induced by hydrogen peroxide in vitro.

Oxidative stress is defined as imbalance between the production and destruction of reactive oxygen species. The aim of this study was to investigate whether resveratrol could protect human endothelial cells against hydrogen peroxide damage in vitro. In this in vitro study on human coronary endothelial cells, the effects of resveratrol on the glutathione content in human coronary endothelial cells in vitro were evaluated with high performance liquid chromatography. The effects of resveratrol on protein expression of the glutamate cysteine ligase, glutathione peroxidase and glutathione reductase enzymes were evaluated with the Western blot method. Resveratrol increased the reduced glutathione contents significantly (p < 0.05). Resveratrol increased protein expression of the glutamate cysteine ligase, glutathione peroxidase-1 and glutathione reductase enzymes (p < 0.05). All data supported each other and suggested that resveratrol had a protective effect against human coronary artery endothelial cell damage. It is thought that these results could pave the way to the new therapeutic approaches to protect against oxidative stress that develops in cardiovascular diseases.

Special-study modules in a problem-based learning medical curriculum: an innovative laboratory research practice supporting introduction to research methodology in the undergraduate curriculum.

We describe the organization of wet-lab special-study modules (SSMs) in the Central Research Laboratory of Dokuz Eylül Medical School, Izmir, Turkey with the aim of discussing the scientific, laboratory, and pedagogical aspects of this educational activity. A general introduction to the planning and functioning of these SSMs is given, along with specific examples. The wet-lab SSMs incorporate several innovative pedagogies: problem-based learning, research-based learning, practical laboratory education, team-based learning, and project-based learning. Oral and written evaluations show that the students find this activity rewarding. The wet-lab SSM model applied in the Research-Lab of Dokuz Eylül School of Medicine represents a format which is effective in training the students in research methodology, practical laboratory work, and independent learning.

In vitro reoxygenation following hypoxia increases MMP-2 and TIMP-2 secretion by human umbilical vein endothelial cells.

Endothelial cells lining the inner blood vessel walls play a key role in the response to hypoxia, which is frequently encountered in clinical conditions such as myocardial infarction, renal ischemia and cerebral ischemia. In the present study we investigated the effects of hypoxia and hypoxia/reoxygenation on gelatinases (matrix metalloproteinase-2 and -9), their inhibitor (TIMP-2) and activator (MT1-MMP), in human umbilical vein endothelial (HUVE) cells. HUVE cells were subjected to 4 h of hypoxia or hypoxia followed by 4 and 24 h of reoxygenation. The pro- and active forms of MMP-2 and MMP-9 were analyzed by gelatin zymography; TIMP-2 protein level was assayed using ELISA, while MT1-MMP activity was measured using an activity assay. The secretion of MMP-2 proform increased significantly in cells subjected to 4 h of hypoxia followed by 4 or 24 h of reoxygenation, compared with the normoxic group. TIMP-2 protein level also increased significantly in the hypoxia/reoxygenation groups, compared with the normoxic group. There were no statistically significant differences in the levels of active MT1-MMP in all groups. This study indicates that MMP-2 and TIMP-2 could be regarded as important components of a mechanism in the pathophysiology of ischemic injury following reperfusion.

Alterations in biochemical components of extracellular matrix in intervertebral disc herniation: role of MMP-2 and TIMP-2 in type II collagen loss.

Alterations in the composition of intervertebral disc extracellular matrix, mainly collagen and proteoglycans, may cause changes in mechanical properties of the disc, leading to dysfunction, nerve root compression, and herniation with severe clinical manifestations. Matrix metalloproteinases may be involved in degradation by hydrolysing extracellular matrix components. Inhibitors of matrix metalloproteinases, in contrast, function in the maintenance of degradation control. In this study, we investigated: (i) whether the level of matrix degradation correlated with the duration of the symptomatic disease, (ii) roles of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) in intervertebral disc degeneration. Nucleus pulposus of intervertebral discs were obtained from 22 patients and analysed for collagen and proteoglycan contents, and pro-MMP-2, TIMP-2 levels. Collagen content was determined as hydroxyproline and proteoglycan content was measured as glycosaminoglycans. The loss in matrix components did not correlate with the duration of the degenerative disc disease. Pro-MMP-2 levels were higher at early stages of the degenerative disc disease (r = -0.495, P < 0.05). TIMP-2 levels were similar in all samples. Pro-MMP-2 and TIMP-2 levels negatively correlated in herniated discs samples (r = -0.855, P < 0.01). Pro- MMP-2 levels negatively correlated with the collagen content in herniated disc material. Our findings may suggest a silent period of active disease prior to symptomatic outcome during which irreversible matrix loss occurs. Involvement of other proteolytic enzymes at different stages of the disease should also be investigated to help to control the degradation cascade at relatively early stages of disc degeneration before the clinical onset of disease.

Effect of D-penicillamine on rat lung elastin cross-linking during the perinatal period.

This study was designed to clarify the effects of D-penicillamine (DPA), a drug used for treatment of various pathological events, on lung elastin formation and maturation of the newborn in the perinatal period. The investigation was conducted on 20 newborn rats bred from 40 female and six male rats. DPA doses 400 mg kg(-1) day(-1) and physiological saline were given intraperitoneally (i.p) to experimental and control groups. To assess newborn maturation, their body and lung weights were determined. Serum Cu levels were measured by atomic absorption spectroscopy and ceruloplasmin (Cp) activities were measured spectrophotometrically. Newborn lung tissue elastin, desmosine (DES) and isodesmosine (IDES) levels were measured by HPLC. The results showed that DPA treatment caused loss of skin elasticity and reduction in body and lung weight in newborns of the experimental group. The serum Cu levels and Cp activity were found to be significantly lower in both maternal and newborn of the experimental groups compared with the control group. The lung DES, IDES and elastin values of newborns in the experimental group were decreased compared with the control group. In conclusion, our results indicate that 400 mg kg(-1) day(-1) DPA, a dose that is used in the treatment of Wilson's disease, rheumatoid arthritis and cystinuria, caused the retardation of newborn maturation, a decrease in DES-IDES cross-links and levels of lung elastin of offspring in the perinatal period. Another conclusion to be drawn from this study is that even low levels of Cu depletion due to DPA administration induces a change in cross-linking in lung elastin during the perinatal period.

In vitro effects of high glucose concentrations on membrane protein oxidation, G-actin and deformability of human erythrocytes.

The object of this study was to examine the effect of elevated in vitro glucose concentrations on protein modification and functional changes in human erythrocytes. Groups were exposed to 5-45 mM glucose concentrations. The time effect of any changes was also evaluated. In erythrocyte ghosts, protein glycation and oxidation were evaluated using spectrophotometric methods. G-actin was measured by a DNase I inhibition assay in cell lysates. Erythrocyte deformability was assessed using a cell transit analyser. At 24 h, a significant protein oxidation (at 25 and 45 mM glucose; p < 0.05), and G-actin increase was observed for all concentrations (p < 0.05). At 48 h, a significant increase in glycation (25 and 45 mM glucose; p < 0.05), protein oxidation (p < 0.05), and G-actin (p < 0.05) was observed in all groups. A significant positive correlation was observed between glucose /protein oxidation, glucose/G-actin and protein oxidation/G-actin at 24 and 48 h. Our findings show that the oxidative effect of glucose on erythrocytes depends on concentration and incubation time. We also present the first evidence of increased G-actin in human erythrocytes exposed to high glucose concentrations as a diabetes model.